sq1<-seq(0,100,length.out=15)
sq2<-sq1[c(1:4,6:9,11:15)]
sq3<-sq1[c(1,3,5,7,9,11,13,15)]
sq4<-replace(sq1,c(2,4,6,8,10,12,14),c(2,4,6,8,10,12,14))